The Veterinary Resources Branch, Division of Research Services established a Watanabe Hyperlipidemic Rabbit (WHHL) breeding colony to be used as a resource for investigators requiring the use of this animal model. The colony is being characterized for serum total cholesterol, cholesterol levels of the lipoprotein fractions and serum triglyceride levels. Blood is being collected from rabbits at the following ages: six weeks, three months, seven months, and one year. Total serum cholesterol values ranged from 310 to 1251 mg/dl with a mean of 828 mg/dl. The low density lipoprotein (LDL) cholesterol values ranges from 1185 mg/dl with a mean of 630 mg/dl. Thus 80% of the total cholesterol was composed of LDL cholesterol. There was a substantial decrease from 885 to 576 mg/dl in serum total cholesterol between the ages of eight weeks and one year. The most significant decrease occurred between the ages of 15 to 25 weeks. There was a no difference in total cholesterol concentrations due to sex. The serum triglyceride values ranged from 107 to 959 mg/dl with a mean of 394 mg/dl. There was an initial increase in triglyceride concentration from 367 to 565 mg/dl between two months and three months of age. However, the serum triglyceride concentration decreased to 349 mg/dl within one year of age. The serum triglyceride concentration was influenced by the sex of the rabbit. The mean male and female serum triglyceride concentrations were 510 mg/dl and 309 mg/dl respectively.